1. Field of the Invention
This invention relates to a data processing device having a voltage detection circuit generally used in a battery-operated microcomputer, electronic desk calculator, electronic notebook or the like.
2. Description of the Related Art
FIG. 1 shows the construction of a voltage detection circuit of a conventional microcomputer or the like. The voltage detecting section of the microcomputer 1 constructed by the integrated circuit (IC) of FIG. 1 is externally supplied with a power source voltage E and a reference voltage V1 divided by a resistor 2 and a zener diode 3. Further, the power source voltage E is divided by resistors 4 and 5 and supplied to a voltage comparison circuit 6 as a to-be-detected voltage V2. The voltage comparison circuit 6 compares the reference voltage V1 and to-be-detected voltage V2 with each other and outputs a detection signal F as the result of comparison.
However, the circuit of FIG. 1 has the following defects.
(a) It is necessary to form the circuit elements 2 and 3 for creating the detection voltage V1 used as a comparison reference outside the IC.
(b) It is necessary to provide terminals T.sub.1 to T.sub.3 used for inputting a reference voltage from the exterior of the IC.
(c) It is necessary to provide the voltage comparison circuit 6 for comparing the reference voltage V1 with the to-be-detected voltage V2.
(d) Only the voltage F is detected.